1. Field of the Invention
The present invention relates to an apparatus and a method for monitoring a glass plate polishing state and a polishing machine comprising the same, and more particularly, to an apparatus and a method for monitoring a glass plate polishing state, which may determine a fault in a polishing state during glass plate polishing using a polishing machine and may provide corresponding information, and a polishing machine comprising the same.
2. Description of the Related Art
Generally, it is very important that a glass (or a glass plate) applied to a liquid crystal display keeps its flatness to a certain level so as to accurately realize images on the liquid crystal display. Accordingly, fine waviness or unevenness on the surface of the glass should be removed through polishing.
A conventional glass plate polishing apparatus includes an upper unit (or an upper plate) having a polishing pad and a lower unit (or a lower plate) where a glass plate will be put, wherein the polishing pad of the upper unit is contacted with the glass plate on the lower unit and the lower unit is rotated while a polishing solution is supplied to the upper unit by free fall, so that the glass plate is polished with the polishing pad. Alternatively, the glass plate polishing apparatus may include an upper unit where a glass plate will be fixed and a lower unit having a polishing pad, wherein the glass plate may be polished with the polishing pad while a polishing solution is supplied to the glass plate.
However, glass plate polishing using the conventional polishing apparatus has difficulty in recognizing a polishing state during polishing. For example, it is difficult to accurately recognize whether a defect such as an impurity or a scratch exists on a glass plate being polished, and where the defect exists on the glass plate, if any. Also, it is difficult to clearly recognize whether an amount of a polishing solution supplied during polishing is large or small, whether a proper polishing pressure is being applied, how much a polishing pad is worn down, and the like. In addition, it is difficult to recognize whether a glass plate in a polishing apparatus is damaged, and where the damaged portion exists on the glass plate, if any.
In particular, with the trend toward mass production and larger size of glass plates, it is more difficult to individually monitor a polishing state for each glass plate.
If a glass plate polishing state is poorly monitored during polishing, the polishing efficiency of the glass plate is reduced and an operator cannot take a proper action when a fault occurs. For example, when a defect such as an impurity or a scratch is not removed but polishing is terminated after the lapse of a preset polishing time, the polishing effect is not obtained. Conversely, when polishing continues up to a preset time even after a defect is removed, the polishing efficiency is reduced and the time and cost is wasted. Moreover, a neglected defect at a specific location of a glass plate due to poor monitoring will affect the subsequent manufacturing process of the glass plate. Also, when a supply amount of a polishing solution is too large, a polishing pad will not have a friction force, and when a supply amount of a polishing solution is too small, the usage effect of the polishing solution will not be obtained. Accordingly, when a polishing solution is not supplied at a proper amount, the polishing efficiency obtained by the polishing solution is not achieved. Also, when the wear of a polishing pad is not monitored, it is difficult to accurately recognize a replacement recycle of the polishing pad. In addition, when it is not monitored whether a polishing pressure of a polishing apparatus is proper, or whether a glass plate is damaged, a polishing state is recognized only after seeing a polished glass plate, resulting in waste of time and cost.